Tính:
(-7)2.6+23.34
112.23+(-3)4.52
132.11+53.24-100
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\(2^7:2^2+5^4:5^3.2^4-3.2^5\\ =2^{7-2}+5^{4-3}.2^4-3.32\\ =2^5+5.16-96\\ =25+80-96=9\)
\(\frac{\frac{2}{3}-0,4-\frac{2}{7}+\frac{2}{11}}{\frac{13}{3}-2,6-\frac{13}{7}+\frac{13}{11}}=\frac{\frac{2}{3}-\frac{2}{5}-\frac{2}{7}+\frac{2}{11}}{\frac{13}{3}-\frac{13}{5}-\frac{13}{7}+\frac{13}{11}}=\frac{2\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}+\frac{1}{11}\right)}{13\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}+\frac{1}{11}\right)}=\frac{2}{13}\)
\(\frac{\frac{2}{3}-0,4-\frac{2}{7}+\frac{2}{11}}{\frac{13}{3}-\frac{2}{6}-\frac{13}{7}+\frac{13}{11}}=\frac{\frac{2}{3}-\frac{2}{5}-\frac{2}{7}+\frac{2}{11}}{\frac{13}{3}-\frac{13}{5}-\frac{13}{7}+\frac{13}{11}}=\frac{2\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}+\frac{1}{11}\right)}{13\left(\frac{1}{3}-\frac{1}{5}-\frac{1}{7}+\frac{1}{11}\right)}=\frac{2}{13}\)
Vậy \(\frac{\frac{2}{3}-0,4-\frac{2}{7}+\frac{2}{11}}{\frac{13}{3}-2,6-\frac{13}{7}+\frac{13}{11}}=\frac{2}{13}\)
a)
\(5A=5+5^2+.....+5^{101}\)
\(\Rightarrow5A-A=\left(5+5^2+.....+5^{101}\right)-\left(1+5+.....+5^{100}\right)\)
\(\Rightarrow4A=5^{101}-1\)
\(\Rightarrow A=\frac{5^{101}-1}{4}\)
b)
\(2B=1+\left(\frac{1}{2}\right)^2+....+\left(\frac{1}{2}\right)^{100}\)
\(\Rightarrow2B-B=\left(1+\frac{1}{2^2}+.....+\frac{1}{2^{100}}\right)-\left(\frac{1}{2}+\frac{1}{2^2}+......+\frac{1}{2^{99}}\right)\)
\(\Rightarrow B=1-\frac{1}{2^{100}}\)